What is Solar Wind

The sun does not keep its energy to itself. Its energy flows away in the form of electromagnetic radiation and particles. The particles (mostly electrons and protons) do not move nearly as fast as the radiation, which escapes the sun at the speed of light, but they move fast nevertheless—at more than 300 miles per second (500 km/s). It is this swiftly moving particle stream that is called the solar wind.
The solar wind is driven by the incredible temperatures in the solar corona. As a result, the gases are sufficiently hot to escape the tremendous gravitational pull of the sun. The surface of the earth is protected from this wind by its magnetosphere, the magnetic “cocoon” generated by the rotation of the earth’s molten core. As with many other planets, the motion of charged molten material in the earth’s core generates a magnetic field around the planet. This magnetic field either deflects or captures charged particles from the solar wind. Some of these particles are trapped in the Van Allen Belts, doughnut-shaped regions around the earth named after their discoverer. Some of the charged particles rain down on the earth’s poles and collide with its atmosphere, giving rise to displays of color and light called aurora (in the Northern Hemisphere the Aurora Borealis, or Northern Lights, and in the Southern Hemisphere, the Aurora Australis, or Southern Lights). The Auroras are especially prominent when the sun reaches its peak of activity every 11 years.